On Monday, the downward spiral of the company that catapulted to trend-setting prominence on the back of Michelle Obama claimed its highest-profile head with the news that Jenna Lyons, officially president and executive creative director of the brand, and unofficially its public face, would be leaving.

The parting was a mutual decision by Ms. Lyons and Millard S. Drexler, the J. Crew chairman and chief executive. She will continue as a creative adviser to the company until her contract runs out in December, but will not be officially replaced.

Instead, Somsack Sikhounmuong, head of women’s design, will become chief design officer, with responsibility for women’s wear, men’s wear and children’s wear (Crewcuts). Unlike Ms. Lyons, however, he will not oversee brand image, store design or marketing. He and other creative teams will report directly to Mr. Drexler.

In other words, there isn’t going to be one primary design vision in charge of all the aesthetic aspects of the brand. Mr. Drexler has talked about a return to core principles at J. Crew, which may include a return to a more anonymous design team as Mr. Sikhounmuong has so far remained resolutely in the background. That doesn’t really sound like a big deal, until you start thinking about its implications — especially when it comes to the accessible, mass-market end of the spectrum.

After all, many would say it’s about time that Ms. Lyons left. J. Crew has been battling a two-year sales slump and is carrying a debt load of $2 billion, some of which will become current in 2018, prompting heightened speculation from investment analysts and news outlets of a possible bankruptcy filing. Same-store sales (purchases in stores that have been open more than a year, a gauge that eliminates the effect of new store openings on sales tallies) have fallen in 11 of the past 12 quarters. Last year, J. Crew shut its bridal business. And last month, the company, which is backed by the private equity firms TPG Capital and Leonard Green & Partners, reported that revenue fell 2 percent, to $695 million, during the three months to Jan. 28. Something isn’t working.

Whispers about the need for design change at the brand began in 2015, when Tom Mora, head of women’s design, was fired and Mr. Sikhounmuong was moved up from his design role at Madewell, the hipper, younger (and growing) brand under the J. Crew umbrella. Yet for most consumer brands, of which J. Crew is one, the designer is almost beside the point; a leader whose name most consumers never know. (Does the Gap have a creative face? L.L. Bean? Target? Ann Taylor? Theory?) Rather, it’s the merchant who matters.

But J. Crew was different.

The company achieved its initial turnaround in part by taking the tools of high fashion and applying them to the mass market. Including — especially — making the designer the embodiment of the brand as a shortcut to authenticity and attitude.

When Mr. Drexler joined J. Crew in 2003, it was effectively a catalog company with some stores that sold preppy staples. He found, buried in the creative team, a young woman named Jenna Lyons. And he had the brilliant idea — because that’s what it was — of transforming her from a cog in the company wheel into its avatar, à la Phoebe Philo at Céline or Karl Lagerfeld at Chanel.

Ms. Lyons — tall, gangly, with a broad grin and thick-framed nerd glasses — put the human factor into generally faceless, accessible fashion. Her geek-chic quirkiness, which mixed camouflage and sequins for day, and denim and taffeta for evening, all of it layered with big costume jewelry, was a model not just for those she worked with, but also for her customers: “Jenna’s picks” were publicized in the catalog and on the website; she was photographed at home in Park Slope, Brooklyn (and later, post-divorce, at home in SoHo); she once appeared in a catalog shoot painting her young son’s toenails pink.

She went where no similar brand had gone before: not just to the Costume Institute Gala at the Metropolitan Museum of Art, where she was widely photographed on the red carpet mixing feathered ball gowns and crew-neck sweaters (and, last year, with Lena Dunham and Jenni Konner of “Girls” both channeling Ms. Lyons’s look), but also into the pages of Vogue, and finally to New York Fashion Week itself, as J. Crew held presentations in the official collection venues. She was an accessible personality whose lifestyle J. Crew customers could, and did, aspire to buy into.

It all culminated in the White House, after Mrs. Obama’s callout to J. Crew on “The Tonight Show with Jay Leno” during the 2008 presidential campaign, a moment orchestrated by Ikram Goldman, proprietor of the high-fashion Chicago boutique Ikram, who at that time was working with Mrs. Obama on her wardrobe. After that election, Malia and Sasha Obama also wore custom-made J. Crew to their father’s swearing-in, while the first lady added J. Crew gloves to her Isabel Toledo coat and dress. Mrs. Obama wore J. Crew on her first state visit, to Britain (an embellished cardigan and mint-green gingham pencil skirt), as well as to the second inauguration (gloves and belt with a Thom Browne coat). Among other appearances.

J. Crew’s woes can to a certain extent be attributed to the same malaise that has hit many of its peers, including Gap Inc., which is also suffering because of growing competition from even-cheaper fast-fashion competitors and an excess of brick-and-mortar stores. But those problems can also be traced to the great fashion experiment.

The trendsetting style element, exciting as it could be, created added confusion: How fashion-forward could a mass-market retailer be? How quirky was too quirky? What happened when people had enough sequins and needed to get serious? Could they look beyond the buzz? Was it expensive or affordable? Where did J. Crew belong?

In the end, consumers couldn’t be bothered with the answers. They just went elsewhere. And the face of the brand became the symbol of its fall.

It’s hard to ignore the lesson.

Jenna Lyons, J. Crew’s president and creative director, at the company’s offices in Manhattan in 2014. Credit Yana Paskova for The New York Times

Jenna Lyons Exits J.Crew

NEW YORK, United States — J.Crew’s Jenna Lyons is exiting the company after 26 years with the specialty retailer, BoF has learned.

"Jenna and I got together and we both agreed it was time for a change,” J.Crew chief executive Millard "Mickey" Drexler told BoF in an exclusive interview. "That being said, she’s got plans to do other things. It’s been a great run. There’s a lot of mutual respect between Jenna and me.”

“It has been beyond my wildest dreams to work with such an amazing team of people at such an incredible brand and alongside Mickey — one of retail’s most talented visionaries,” Lyons said in a statement. "I am excited about the next chapter for J.Crew as well as the opportunity for other creative leaders within the organisation to step up and take on new responsibilities. Having spent the better part of my life with J.Crew, I feel an immense pride and love for everyone at the company.”

Current J.Crew women’s head of design Somsack Sikhounmuong — who previously led sister label Madewell’s design and has been with the company since 2001 — will be promoted to chief design officer, overseeing the women’s, men’s and children's design teams effective immediately. All other creative departments that were reporting to Lyons — who was also president of the company — will now report to Drexler. Lyons will stay on as a creative advisor until the end of her current contract, which expires in December 2017.

"Somsack and our design teams have a deep understanding of the aesthetic and style our customers rely on us to deliver, with a proven track record of driving creative vision in-line with our brand DNA,” Drexler said. "We are excited to extend Somsack’s vision across all design categories and look forward to the team’s contributions. As always, delivering the very best product, value and brand experience across channels is our top priority.”

Lyons joined J.Crew in 1990, although her role was elevated after Drexler came on board in 2003. Through their unique partnership, they transformed J.Crew into a cultural phenomenon, shaping the way an entire generation of American men and women dress, with Lyons' energised, tongue-in-cheek take on classic preppy tropes. Her candy-coloured designs — from the now-classic "Bubble" necklace to the "No. 2" pencil skirt — impressed themselves on current fashion in a way rarely seen at the mass level. In 2010, Drexler promoted her to president, reflecting her growing influence in design at the company.

Along the way, Lyons became something of a cultural icon in her own right, someone whose personal style — statement eyewear, oversized suiting, sequins for day — was copied the world over. Just this past Friday, Lyons was captured on J.Crew’s Instagram handle celebrating the retailer’s self-made holiday, National Stripes Day.

However, some say that more recently Lyons' role had transitioned from day-to-day design duties as she became more of a public a face for the brand. And, like many specialty retailers, J.Crew has been squeezed by discount culture, the casualisation of dress and the consumer's penchant for fast fashion, which relies less on one well-defined aesthetic and more on moving trends quickly to the market.

The impact of these market forces have weighed on the company's results. In its 2016 fiscal year, net sales at J.Crew were $2 billion, down 6 percent from the previous year. Sales at stores open at least one year were down 8 percent. Turnaround efforts — including a return to the preppy “basics” that performed so well in the past and a move into athleisure with a multi-season collaboration with New Balance — have yet to move the needle.

The company’s top line has been boosted somewhat by the growth of Madewell, which saw net sales in 2016 increase 14 percent to $341.6 million, with comparable sales up 5 percent. But the company's debt — which totalled $1.5 billion, net of discount and deferred financing costs, at the end of last year — has proven an albatross, and has reportedly led the company to consider a debt restructuring.

Indeed, this announcement is expected to be the first in a series of strategic changes that will allow it to perform in its next iteration. As for Lyons' post-J.Crew plans, these are not yet known. The indelible mark she has made in defining American fashion for the past decade cannot go unacknowledged.

Jenna Lyons is leaving J.Crew. Long live Jenna Lyons

The world of fashion is filled with comings and goings. Nowadays, it’s common for a creative director to spend a few years with one label, before moving on to another. Who’s designing at Dior now? And what of Valentino? For everyday American women—even those who love to get dressed—the answer isn’t relevant.

But most could name the creative force behind J.Crew: Jenna Lyons. Which is why yesterday, when my phone dinged with a message from a colleague: “Did you see this?” and a link to the news that Lyons would be leaving J.Crew, after 26 years rising through the company’s ranks to the role of president and creative director—second only to CEO Mickey Drexler—it felt, almost laughably, like a moment I might look back on: “Where were you when you found out Jenna was leaving?” (I was, no kidding, at the Trevi Fountain in Rome, wearing my navy J.Crew menswear-style wool jacket. This brand is always with us.)

J.Crew is a company that many people, myself included, feel a deeply personal connection with. As a high-schooler in St. Louis, MO in the 1990s, I would wait for the catalogue and turn down the corners of pages showing the barn jackets, rugby shirts, and roll-neck sweaters I longed for. Twenty years later, I repeatedly lamented that a favorite piece from that era—a simple, scoopback one-piece swimsuit—was impossible to find. At the time, J.Crew was making headlines by directly responding to customer feedback, and my editor at The Cut encouraged me to write an open letter to Lyons. The Cut published my letter, and Lyons’ reply landed swiftly in my inbox, alluding to a possible return of the style the following summer: “I really do appreciate your letter—could never have described that swimsuit better and it is a great reminder to us all that we still have some relics from our past collections that are worth revisiting.”

The following summer, the swimsuit was resurrected, with fanfare. The outpouring of tweets, emails, and texts I received from gushing and grateful fellow fans of the scoop-back tank suit was overwhelming. Jenna Lyons made me a hero. (Truth told, I suspect she might have had plans to resurrect that swimsuit regardless.)

It was my first glimpse behind the scenes at Jenna Lyon’s J.Crew—a place more progressive, playful, and fashion-forward than the J.Crew of my childhood, though its preppy spirit remained very much intact. I returned there last February, when I was invited to participate in a cast of non-professional models in the brand’s Fall 2017 show. A few days before, I arrived to J.Crew’s offices for my fitting. There, I found oldies piping through the speakers, and racks upon racks of rainbow-ordered tweeds, furs, sweaters, and plaids.

My outfit—or “look,” in industry parlance—had already been selected and hung waiting for me: medium-wash blue jeans, a striped wrap blouse, a slate velvet blazer, and a vibrant red wool coat. I put it all on, and Somsack Sikhounmuong—then head of womenswear, and now the chief design officer—and Gayle Spannaus, J.Crew’s longtime superstar stylist, worked in tandem with Lyons. I was drowning in layers, so I first removed the red coat. Wrong move; Lyons could see we needed the color. The blazer came off, and when I went to put my arm through the red coat’s sleeve, Lyons stopped me and tossed it over my shoulders instead. A silk foulard scarf appeared, and I stepped into a pair of plaid block heels. Spannaus advised skipping a bra come show day: It’s better to see a human breast than a bra, she said. Lyons told me not to bother with a manicure.

“We want you to look like you,” she said, snugging the coat around my shoulders.

One could easily see Lyons’ departure as the end of an era. But the mark she left goes far beyond J.Crew, or even fashion. Jenna Lyons’ impact is about style and attitude as much as it is about clothing. To watch her work—or to read about it—is to see the way she empowers those around her, whether by making the resurrection of a classic swimsuit seem like it was your genius idea, or emboldening women to treat leopard spots as a neutral, menswear as womenswear, and pajamas as clothes.

Lyons will stay on at J.Crew as a creative advisor through the end of the year, but please let’s not eulogize the Jenna Lyons era of American fashion. As far as I’m concerned, it’s far from over. Lyons has left us with loads of lessons: Perfect is boring; socks and bras are overrated; stripes are underrated; if you’re super-formal on the bottom (ie: ballgown skirt) go more casual up top. And above all, getting dressed should be fun, and make you feel like you.

I suspect Lyons’ very qualified cohorts at J.Crew will be channeling their “inner Jenna” for years to come—asking themselves “What would Jenna do?” (WWJD)—just as I did yesterday at a vintage store in Rome, when I fell in love with a lusciously soft wool checked blazer that was just a smidge too big for me.I pulled my arms out of the sleeves, and tossed it over my shoulders instead.